It is common in longwall mining to transport the cut coal from the shearing face of the seam by way of a so-called armored face conveyor or “AFC” in order to move high tonnages of coal from the area of the mining machine to a main conveyor belt and then out of the mine. A typical AFC is made up of a number of interconnected line pans having profiled side channel guides, commonly referred to as “sigma sections”, so named due to the close similarity of their cross-sectional configuration with that of the capital Greek letter. A plurality of elongated flight bars, interconnected by one or two continuous chains, lie transverse across the conveyor and slide along the flight pans to move the cut coal therein. The ends of the flight bars are specially profiled to slidably fit within the contoured sigma sections of the line pans and are guided with minimum friction therein, while wedging of material is also minimized. The flight bars are dragged along the line pan by the attached endless chains which, in turn, are driven by powerful motors.
As can be appreciated, there is a great deal of sliding contact between the profiled ends of the flight bars and the similarly contoured and closely fitting sigma sections of the line pans. After a period of time, the end portions of the flight bars become worn down to a degree that excessive clearances develop between the flight bar end portions and the sigma sections and the required guidance provided by the sigma sections is no longer present. When this condition develops, the worn flight bars shift and misalign which can cause line breakage and equipment shut-down if the problem is not corrected.
It has been common practice in the coal mining industry to remove and scrap the worn flight bars and replace them with flight bars in a newly manufactured condition. Needless to say, this is an expensive practice which has received some considerable attention in the past, but has yet to be rectified in a quick efficient manner until the present invention.
Prior attempts to repair worn flight bars have not proved entirely successful. One such repair method proposed to build-up or reconstruct the worn bar ends by hardforming, that is, by direct weld deposition on the worn areas of the flight bar. If the amount of deposited weld material becomes too great in certain areas, it has been found that the hardness of the surface coating will vary, which proves troublesome due to differential wearing. It is also very expensive and difficult to duplicate the complex surface profile geometry of the original flight bar tip by welding or hardforming. When the original bar-end profile is not duplicated to a substantial degree, the repaired flight bar will cause objectionable increased wear or jamming in the profiled sigma sections of the line pans. Hence, the desired smooth running chain scraper operation will not be realized.
Other attempts to provide replaceable flight bar ends utilize a dedicated set of fasteners to attach the bar ends to the flight bar. Such a construction increases the number of parts that must be used, the likelihood that a nut or bolt could be dropped or lost during replacement, and, in some designs, places considerable stress on the fastener itself.
The present invention solves the problems previously encountered by providing a replaceable bar end having substantially the same outer profile as the original design that can be quickly replaced without welding or cutting off the existing bar end, and which is secured to the flight bar body using the same fasteners that secure the bar body to the chain. Furthermore, because the replaceable bar end is mechanically attached to the body it can be produced out of the most desirable material and can have different mechanical properties and chemistry than those of the material used for the flight bar body, without the restriction of it being a weldable material. Such mechanical properties include tensile yield, elongation, reduction of area, and hardness, and specific chemistries utilized to affect the mechanical properties are generally known in the art. This allows the selection of a highly wear resistant material for the bar end.